I actually tried to get the blue duct pipe as suggested but couldnt find anywhere locally that stocked it and online i could only find people that wanted crazy (£40) delivery charges. I had a few lengths of soil pipe in the garden doing nothing so it was a way forward. Granted its not the water duct pipe but the soil will allow a new pipe to be pulled on the extremely off chance it is ever needed. Most people just bury the pipe in the ground. .